Several industries desire composite structures or parts for their high strength and lightweight. The aircraft industry, for example, uses composite structures to make lightweight structural components.
Many approaches have been previously developed for forming multiple layers of composite material into a desired shape or shapes. The most common, particularly in the aircraft industry, involves placing individual layers of material onto a form having a desired shape, and then curing the layers. Curing the material through application of heat and pressure fully compacts or debulks the composite material. The cured composite material then has the desired shape and strength. Forming parts in this way does not involve significant reshaping of the composite material during curing and may be very time consuming.
Disadvantages inherent in the aforementioned process include the very tedious and time consuming operation of laying individual layers of composite material directly onto a tool to obtain a final, non-flat desired shape. The very labor intensive process of placing the layers of material onto a form may require many highly-skilled man-hours for each part, and is, therefore, very expensive.
Additionally, the aforementioned process may require stopping after placement of every few layers of material and providing some form of mechanical compaction to the material. This may be necessary to achieve final full compaction of the layers. Failure to achieve full compaction of the material layers prior to curing may result in wrinkles and other anomalies in the final structure, since as individual layers compact, the local path-lengths of the fibers in the layers change. Wrinkles and other anomalies in the cured structure are aesthetically and structurally undesirable.
Previously developed methods for forming composite parts also fail to assure uniformity between parts. In the prior art, each part is separately made. Each part is formed by the process of placing individual layers onto a form, and then curing the layers while on the form. The cured part is removed from the form allowing the next part to be made by-the same process. By this method a number of parts can be formed. Unfortunately, variations in compaction, in resin bleeding from the part, and in fiber "washing" or dislocations from resin bleeding, tend to occur because compaction is occurring three dimensionally, and because of the low viscosity of the resin. These factors may yield parts that lack uniformity. Previously developed methods for building composite parts are, therefore, not compatible with low-cost, high-volume manufacturing methodologies.
Composite parts fabricated by previously developed methods often require machining after curing, e.g., routing, grinding, etc., in order to meet final dimension requirements. This machining adds additional time and expense to the process of fabricating the part and can result in damage to the part by delamination of the cured layers.
Yet another disadvantage of the previously developed methods for fabricating composite parts is their incompatibility with in-process control (IPC), statistical process control (SPC), and total quality (TQ) methodologies. IPC, SPC and TQ require repeatable, measurable results to obtain full effectiveness. The custom approach of the prior art to fabricating composite parts is not amenable to obtaining the benefits of IPC, SPC and TQ, i.e., high quality, high yield, and low cost.
Previously developed methods for forming composite parts often do not provide acceptable results when forming complex parts from two or more sub-parts or pre-forms by "co-curing". In co-curing, two or more sub-parts are made into a single part by placing the sub-parts in the desired orientation and curing the combination. Since the prior art requires the individual layers of a sub-part to be laid-up in their final shape on a form, joining two or more individual sub-parts to make a part, e.g., two channels and two plates to form an I-beam, is very difficult. If a foreign material, e.g., backing paper or tape, is accidentally trapped between the layers during layup of a part, there is little likelihood that it will be detected. As a result, high labor costs may be invested in a complex, co-cured part that must be scrapped due to the inclusion.
Prior methods for fabricating composite parts often require that the individual composite layers be stored in a freezer prior to lay-up. This adds additional handling and equipment costs in fabricating a composite part.
Therefore a need has arisen for an improved method and system for fabricating parts from composite materials.
A need further exists for an improved method and system for reducing the time necessary for fabricating composite parts.
A further need exists for a low-cost method and system for fabricating parts from composite materials.
Yet another need exists for a method and system for fabricating multiple uniform parts from composite materials that do not require significant amounts of machining after curing.
Another need exists for a method for fabricating composite parts compatible with IPC, SPC, and TQ.
An additional need exists for a method and system for fabricating complex three-dimensional parts from composite materials.
Yet another need exists for a method and system for fabricating composite parts that eliminate the need for special handling and storage of composite layers.